In conventional 3rd Generation (3G) Cellular Networks, Point-to-Point (PtP) and Point-to-Multipoint (PtM) paging mechanisms need to provide efficient use of radio paging resources while maintaining low User Equipment (UE) power consumption. Paging is used to establish connections and initiate transmissions. For PtP services, a paging signal that is transmitted to a UE is associated a unique identity assigned to the UE. It is expected for UEs to be in an inactive paging state for considerable time periods while awaiting paging indications. Thus, it is necessary to minimize power consumption while the UEs are in such a paging state. To accomplish this, paging occasions are predetermined in the UE and network. This allows the UE to minimize transmit and receive processing between paging occasions, which results in reduced power consumption and correspondingly increased battery life.
For PtP services, a physical paging channel and paging occasion is determined from identities unique to each UE. A motivation for using UE identities is to provide a substantially equal distribution of paging transmissions across all paging resources.
System Information Block type 5 (SIB 5) defines common channels to be employed in an “idle” mode, and SIB 6 defines common channels for a “connected” mode. In a cell, one or more Paging Transport Channels (PCHs) may be established. Each Secondary Common Control Physical Channel (SCCPCH) indicated to the UE in system information may carry up to one PCH. Thus, for each defined PCH there is one uniquely associated Page Indicator Channel (PICH) also indicated. When more than a single PCH and associated PICH are defined in SIB 5 or SIB 6, the UE selects a SCCPCH from the ones listed in SIB 5 or SIB 6 based on an International Mobile Subscriber Identity (IMSI) as follows:Index of selected SCCPCH=IMSI mod K;  Equation (1)where K is equal to the number of listed SCCPCHs which carry a PCH (i.e., SCCPCHs carrying a Forward Access Channel (FACH) only shall not be counted). These SCCPCHs are indexed in the order of their occurrence in SIB 5 or SIB 6 from 0 to K−1.
Thus, the UE selects a physical paging channel from a list of paging channels according to a Selected Paging Channel Number as follows:Selected Paging Channel Number=UE identity mod K;  Equation (2)where K is the number of physical paging channels that exist within the cell. Equation (2) randomly distributes UEs between the paging channels.
The UE may use Discontinuous Reception (DRX) in idle mode or connected mode in order to reduce power consumption. When DRX is used, the UE needs only to monitor one Page Indicator (PI) in one Paging Occasion per DRX cycle. The UE may be attached to different Core Network (CN) domains with different CN domain specific DRX cycle lengths. The UE stores each CN domain specific DRX cycle length for each CN domain the UE is attached to and use the shortest of those DRX cycle lengths. The DRX cycle lengths to use for Universal Terrestrial Radio Access Network (UTRAN) connected mode is the shortest of the following:
(1) the UTRAN DRX cycle length; or
(2) any of the stored CN domain specific DRX cycle lengths for the CN domains the UE is only attached to with no signaling connection established.
The UE uses the IMSI, the number of available SCCPCH which carry a PCH (K), the Cell System Frame Number (SFN), Np, frame offset, Paging Block Periodicity (PBP) and the DRX cycle length to determine the paging occasions.
For Frequency Division Duplex (FDD), Np is the number of page indicators within a frame, and the frame offset is equivalent to zero. In FDD, the UE monitors its paging indicator in the PICH frame with SFN given by the Paging Occasion.
For Time Division Duplex (TDD), Np is the number of page indicators within a paging block and PICH frame offset values are given in system information.
In TDD, the UE monitors its paging indicator in the paging block given by the paging occasion. The paging occasion gives the SFN of the first frame of the paging block.
The value of the Paging Occasion is determined as follows:Paging Occasion={(IMSI div K) mod (DRX cycle length div PBP)}*PBP+n*DRX cycle length+Frame Offset;  Equation (3)where n=0, 1, 2 . . . as long as SFN is below its maximum value. The actual Page Indicator within a Paging Occasion that the UE shall read is similarly determined based on IMSI.
The Page Indicator to use is calculated by using the following formula:PI=DRX Index mod Np;  Equation (4)where DRX Index=IMSI div 8192.
In TDD mode, the Paging Message Receiving Occasion is calculated using the following formula:Paging Message Receiving Occasion=Paging Occasion+NPICH+NGAP+{(DRX Index mod Np) mod NPCH}*2;  Equation (5)where the value NPICH is the number of frames for PICH transmission and is equal to the PICH repetition length given in system information. The value NGAP is the number of frames between the last frame carrying PICH for this Paging Occasion and the first frame carrying paging messages for this Paging Occasion. The value NPCH is the number of Paging Groups. NPCH and NGAP are given in system information.
Thus, the UE determines the paging occasion, identified by a unique radio frame number, on the selected PICH according to:Paging Occasion Frame Number={UE identity div K} mod {DRX Cycle Length}+n*{DRX Cycle Length};  Equation (6)where DRX is Discontinuous Reception.
Equation (6) identifies the frame number within each DRX cycle and then for each following cycle.
In TDD systems, paging block periodicity and frame offset are also taken into account. A motivation for using UE identities is to provide an approximately even distribution of paging transmissions across all paging resources.
FIG. 1 illustrates a problem with group paging where the UE will likely have to receive separate paging occasions and physical paging channels for reception of user group and UE specific paging. In FIG. 1, “UP” 105 represents a UE specific paging occasion; “GP” 110 represents a User Group paging occasion; and “X” 115 represents UE in DRX. A more efficient method for performing group paging is desired.